(a) Field of the Invention
This invention is concerned with the measurement of fuel in the fuel tanks of the airplane together with the visual inspection of the fuel, so measured for water and other impurities, which inspection is made from the ground on the underside of the wing. Previous to this invention the fuel tank cap on the top side of the wing had to be opened and the fuel level in the tank visually verified. If the level is not immediately apparent then a dip stick has to be inserted into the opening and the amount of fuel in the tank estimated from the mark on the dip stick.
Since fuel is lighter than water and most other contaminants, a check for impurities cannot be made from the top side of the wing. The pilot or other inspector must drain a sample of fuel from the drain sump valve on the underside of the wing to check for the presence of water and other pollutants. Aviation fuel is color-coded by octane. However, if different grades of octane fuel are mixed, the colors usually cancel each other out, resulting in a clear mixture. But a check to determine how much fuel is in the wing tanks can only now be made from the topside of the wing and the fuel tank cap must be taken off and a visual inspection made of the tank or a dip stick used. Inclement weather and slippery conditions could make this inspection difficult and hazardous since it requires climbing onto the wing and removing the fuel caps to ascertain the fuel level. This invention allows both checks to be made at the same time, or even separately, from the convenient safety of the underside of the wing.
(b) Description of the Prior Art
Standard procedure on all aircraft involves at least two (2) separate tests, one for fuel level, the other for water and other contaminants, each test separately taken from only different parts of the aircraft. It can, and often does, involve the safety of the person on top of the wing both in getting there and staying there, not to mention the necessity of opening and securing the fuel caps. No device is currently available which would be more reliable, accurate or convenient.
One sort of present test for fuel level involves a pipette like device which is placed into the fuel tank with the cover removed either pre-calibrated or used with a calibration card. The AOPA Air Safety Foundation Airmanship Refresher Course advises its members not to take for granted the fuel quantity gauges for granted but to always make a visual check of the fuel. In an October 1979 newslatter of the same AOPA, located in Washington, D.C., it advises its members that if they don't have a way of peering into the high wing fuel tanks think about carrying a small light-weight ladder to carry with them. If that's impractical, they advise their members, borrow the FBO's ladder. Checks for pollutants are advised to be made by draining the tank by using the fuel tank sump valve.
Considering the inconvenience of making visual checks of the fuel level and especially if it has to be made during bad weather no doubt such inspection has been "overlooked" in the past. And bad weather must result in its quota of accidental injuries.